The gum resin of the plant Boswellia serrata Roxb. (Burseraceae) has long been in use for the treatment of rheumatoid arthritis and gout by the practitioners of Ayurvedic medicines in the Indian system of medicine. Various extracts of the gum resin have shown potent anti-flammatory and anti-arthritic activity in laboratory animals, as well as during clinical trials ((Atal, C. K., Singh, G. B., Batra, S. and Gupta, O. P., Ind. J. Pharm, 12, 59 (1980); Pachnanda, V. K. Shahikant, Singh, D. and Singh, G. B., Ind. J. Pharm, 13, 63 (1981). In a detailed pharmacological study, Singh et al have established that the alcoholic extract of B. serrata gum resin displayed marked anti-flammatory activity in carrageenan induced oedema in rats and mice and dextran oedema in rats (Singh, G. B. and Atal. C. K., Agent and Action, 18 407, (1986).
It has also been recognized in the past that the ethanolic extract of the gum resin of B. serrata inhibits the formation of Leukotriene B4 in rat peritoneal neurophils. Leukotriene B4 is one of the important mediators of inflammatory reactions [Ammon, H. P. T., Mack, T., Singh, G. B. and Safayhi, H., Planta Medica, 57, 203 (1991).]
The gum resin from Boswellia serrata Roxb. (Burseraceae) is a complex mixture of various terpenoids, polysaccharides and inorganic salts. The polysaccharides and inorganic salts constitute one of the major parts of the said gum. The terpenoids part constitute both lower and higher terpenoids. The lower terpenoids which constitute mainly the monoterpenoids are obtained by steam distillation of the gum resin.
The higher terpenoids fraction which is pharmacologically active is a mixture of various di- and triterpenoids. It has now been established that the anti-flammatory activity of this fraction is due to the presence of certain triterpenoids commonly known as boswellic acids. Boswellic acids are penta cyclic triterpenic acids belonging to the class of ursane group of triterpenoids [Bischof, B, Jerger O, and Ruzicka L., Helv. Chim, Acta, 32, 1911 (1949), and Grham, A. G. Phytochemistry, 7, 963 (1968).]
Two general methods of isolation and separation of boswellic acids from the gum resin of the said plant are chemical and chromatographic. In one of the chemical methods which is described by Winterstein et al [Winterstein, A. and Stein, G., Z. Physiol. Chem., 208,9 (1932) and J. Am. Chem. Soc, 74,3179 (1952)], the gum exudate is extracted with solvent ether and the total acids are precipitated as barium salts using barium hydroxide as the precipitant. The salts obtained are then directly converted into their acetates by heating it with acetic anhydride and pyridine. The boswellic acids
The disadvantage of this method is that the acids are not isolated in their natural forms, but are isolated as their acetates.
In the chromatographic method, defatted ethanolic extract of the gum resin of the said plant is subjected to repeated column chromatography over silica gel and elution with organic solvents such as chloroform, methanol in different proportions furnishes individual boswellic acids in pure form.
The method suffers from the disadvantages of being cumbersome, time consuming and unsuitable for large scale preparations.
New boswellic acid compositions, particularly those possessing unexpected therapeutic properties, and methods for the preparation thereof, would be highly desired by research and industry. The present invention provides such a result.